Seen by NASA's Cassini spacecraft within the vast expanse of Saturn's rings, Prometheus appears as little more than a dot. But that little moon still manages to shape the F ring, confining it to its narrow domain.

Prometheus is caught in the act of creating gores and streamers in the F ring. Scientists believe that Prometheus and its partner-moon Pandora are responsible for much of the structure in the F ring as shown by NASA's Cassini spacecraft.

Saturn's moon Prometheus orbits near some of its handiwork in the F ring in this image from NASA's Cassini spacecraft. Prometheus and its partner Pandora gravitationally sculpt and maintain the narrow F ring.

Although their gravitational effects on nearby ring material look quite different, Prometheus and Pan are both shepherd moons, holding back nearby ring edges in this image captured by NASA's Cassini spacecraft.

Saturn's small, potato-shaped moon Prometheus appears embedded within the planet's rings near the center of this view from NASA's Cassini spacecraft while the larger moon Mimas orbits beyond the rings.

Saturn's moon Prometheus casts a narrow shadow on the rings near the much larger shadow cast by the planet in this image taken by NASA's Cassini spacecraft about five months after Saturn's August 2009 equinox.

Saturn's small moon Prometheus, slightly overexposed in this image taken by NASA's Cassini spacecraft, shows off its potato-like shape as it orbits in the Roche Division between the A ring and thin F ring.

NASA's Cassini spacecraft captured Saturn's moon Prometheus, orbiting near the streamer-channels it has created in the thin F ring, casts a shadow on the A ring in this image taken a little more than a week after the planet's August 2009 equinox.